U.S. patent application number 14/724397 was filed with the patent office on 2016-12-01 for photomask pellicle.
The applicant listed for this patent is Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Chia-Chun Chung, Chia-Hao Hsu, Chih-Tsung Shih.
Application Number | 20160349609 14/724397 |
Document ID | / |
Family ID | 57398409 |
Filed Date | 2016-12-01 |
United States Patent
Application |
20160349609 |
Kind Code |
A1 |
Chung; Chia-Chun ; et
al. |
December 1, 2016 |
PHOTOMASK PELLICLE
Abstract
A method includes providing a carrier wafer, forming an indented
portion on the carrier wafer, the indented portion having a sloped
portion at an edge of the indented portion, bonding a pellicle
wafer on the carrier wafer so as to form an open area within the
indented portion, patterning the pellicle wafer to form a pellicle
membrane over the indented portion and a pellicle membrane support
structure over the sloped portion, and applying a mechanical force
to disconnect the pellicle membrane from the pellicle wafer.
Inventors: |
Chung; Chia-Chun; (Hsin-Chu,
TW) ; Hsu; Chia-Hao; (Hsinchu City, TW) ;
Shih; Chih-Tsung; (Hsinchu City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Taiwan Semiconductor Manufacturing Company, Ltd. |
Hsin-Chu |
|
TW |
|
|
Family ID: |
57398409 |
Appl. No.: |
14/724397 |
Filed: |
May 28, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03F 1/64 20130101; G03F
1/62 20130101; G03F 1/38 20130101 |
International
Class: |
G03F 1/62 20060101
G03F001/62; G03F 1/76 20060101 G03F001/76; G03F 1/80 20060101
G03F001/80; G03F 1/50 20060101 G03F001/50 |
Claims
1. A method comprising: providing a carrier wafer; forming an
indented portion on the carrier wafer, the indented portion having
a sloped portion at an edge of the indented portion; bonding a
pellicle wafer on the carrier wafer so as to form an open area
within the indented portion; patterning the pellicle wafer to form
a pellicle membrane over the indented portion and a pellicle
membrane support structure over the sloped portion; and applying a
mechanical force to disconnect the pellicle membrane from the
pellicle wafer.
2. The method of claim 1, wherein forming the indented portion
comprises: forming a spacing layer on the carrier wafer, and
patterning the spacing layer to form the indented portion.
3. The method of claim 1, wherein patterning the pellicle wafer
further comprises forming a break-off part over the sloped portion
on an opposite side of the pellicle membrane support structure from
the pellicle membrane.
4. The method of claim 1, further comprising, bonding a photomask
to the pellicle membrane support structure.
5. The method of claim 4, wherein the photomask comprises a
pellicle frame attached thereto, and wherein bonding the photomask
to the pellicle membrane support structure comprises bonding the
pellicle membrane support structure to the pellicle frame of the
photomask.
6. The method of claim 1, wherein forming the spacing layer
comprises: depositing a spacing layer material; and performing an
etching process to form the indented portion.
7. The method of claim 1 wherein the indented portion has a
substantially rectangular shape from a top perspective.
8. The method of claim 7, wherein a first dimension of the indented
portion is within a range of about 132-137 millimeters and a second
dimension of the indented portion is within a range of about
104-110 millimeters.
9. The method of claim 1, further comprising, forming an exhaust
port extending from the indented portion to an edge of the carrier
wafer.
10. The method of claim 1, further comprising, before patterning
the pellicle wafer, thinning down a backside of the carrier
wafer.
11. A method comprising: forming an indented portion on a carrier
wafer, edges of the indented portion having a sloped portion
sloping from a lower portion of the indented portion to a top
surface of the spacing layer; bonding a pellicle wafer on the
carrier wafer; patterning the pellicle wafer to form a pellicle
membrane over the indented portion, a pellicle membrane support
structure over the sloped portion, and a break-off part over the
sloped portion; applying a mechanical force to break the break-off
part and disconnect the pellicle membrane and pellicle membrane
support structure from the pellicle wafer.
12. The method of claim 11, wherein forming the indented portion
comprises: depositing a spacing layer material on a carrier wafer
to form a spacing layer on the carrier wafer; and patterning the
spacing layer to form the indented portion.
13. The method of claim 12, wherein a thickness of the spacing
layer is within a range of about 500-600 nanometers, and wherein
the spacing layer comprises at least one of silicon nitride or
silicon oxynitride.
14. The method of claim 11, wherein the break-off part and the
pellicle membrane have a same thickness.
15. The method of claim 11, wherein the break-off part comprises a
trench within the pellicle wafer, the trench surrounding the
pellicle membrane support structure.
16. The method of claim 11, further comprising, bonding a pellicle
frame of a photomask to the pellicle membrane support
structure.
17. The method of claim 11, wherein bonding the pellicle wafer to
the spacing layer comprises a fusion bonding process.
18. An apparatus comprising: a photomask having a patterned
portion; a pellicle frame connected to the photomask, the pellicle
frame substantially encompassing the patterned portion; and a
pellicle comprising: a pellicle membrane support structure shaped
according to the pellicle frame, a first end of the pellicle
membrane support structure being bonded to the pellicle frame; and
a pellicle membrane at a second end of the pellicle membrane
support structure, the pellicle membrane substantially covering the
patterned portion.
19. The apparatus of claim 18, wherein the pellicle membrane
support structure and the pellicle membrane form a monolithic
structure.
20. The apparatus of claim 18, further comprising, a portion of a
break-off part extending from the pellicle membrane support
structure and being coplanar with the pellicle membrane.
Description
BACKGROUND
[0001] In the semiconductor integrated circuit (IC) industry,
technological advances in IC materials and design have produced
generations of ICs where each generation has smaller and more
complex circuits than the previous generation. In the course of IC
evolution, functional density (i.e., the number of interconnected
devices per chip area) has generally increased while geometry size
(i.e., the smallest component (or line) that can be created using a
fabrication process) has decreased. This scaling down process
generally provides benefits by increasing production efficiency and
lowering associated costs. Such scaling down has also increased the
complexity of IC processing and manufacturing.
[0002] Photolithography processes typically form a patterned resist
layer for various patterning processes, such as etching or ion
implantation. In the photolithography process, a photomask (or
mask) is used. The mask includes a substrate and a patterned layer
that defines an integrated circuit to be transferred to a
semiconductor substrate during the photolithography process. During
the formation of the mask or the photolithography process utilizing
the mask, various mask contaminants, such as chemical contaminants,
are introduced and are hard to remove. The current cleaning methods
do not efficiently remove the mask contaminants and may further
damage the mask.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0004] FIGS. 1A-1K are diagrams showing an illustrative process for
forming a pellicle on a photomask, according to one example of
principles described herein.
[0005] FIG. 2 is a diagram showing illustrative dimensions of a
pellicle and other components used to form the pellicle, according
to one example of principles described herein.
[0006] FIG. 3 is a flowchart showing an illustrative method for
forming a pellicle for a photomask, according to one example of
principles described herein.
DETAILED DESCRIPTION
[0007] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0008] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures.
[0009] The apparatus may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein may likewise be interpreted accordingly.
[0010] As described above, during the formation of the mask or the
photolithography process utilizing the mask, various mask
contaminants, such as chemical contaminants, are introduced and are
hard to remove. According to the present example, a pellicle is
formed to protect the mask. Specifically, a pellicle is formed into
a wafer and then bonded to a pellicle frame that is connected to a
mask. Then, the pellicle is mechanically disconnected from the
wafer into which it was formed.
[0011] FIGS. 1A-1K are diagrams showing an illustrative process for
forming a pellicle on a photomask. According to the present
example, FIG. 1A illustrates a spacing layer 104 that is formed on
a carrier wafer 102. The carrier wafer 102 is a sacrificial
structure used to support another layer, in this case, the spacing
layer 104 and subsequently formed layers that will be described in
further detail below. The carrier wafer 102 may be circular. The
carrier wafer 102 may be made of a semiconductor material or other
suitable material.
[0012] The spacing layer 104 may be deposited onto the carrier
wafer 102 using a high density plasma Chemical Vapor Deposition
(CVD) process. In one example, the spacing layer 104 may have a
thickness that is greater than 500 nanometers. In one example, the
spacing layer 104 may have a thickness within a range of about 500
to 600 nanometers. The spacing layer 104 may be made of a material
such as silicon nitride or silicon oxynitride. Such material may be
patterned to create a desired structure as will be described in
further detail below.
[0013] FIG. 1B illustrates a patterning process performed on the
spacing layer 104. The patterning process may be performed using
photolithographic processes and etching processes. Such etching
processes may involve a combination of wet etching and dry etching
to achieve the desired profile. As illustrated the spacing layer
104 is patterned to form an indented portion 106. In the present
example, the indented portion 106 is formed by removing the spacing
layer 104 entirely to expose the underlying carrier wafer 102. The
edges of the indented portion 106 are formed to have sloped
portions 108.
[0014] The profile of the sloped portions 108 can be achieved using
various combinations of wet etching and dry etching. Wet etching
uses chemical etchants to remove material. Wet etching is isotropic
and thus will generally etch in all directions. Dry etching, such
as plasma etching, involves a bombardment of ions to remove
material. Dry etching is anisotropic and thus etches primarily in a
single direction. In the present example, the sloped portions 108
are substantially linear. In some examples, however, the sloped
portions 108 may have other forms. For example, the sloped portions
may be slightly convex or slightly concave. In some cases, only
parts of the sloped portions 108 may be convex or concave while
other parts are substantially linear.
[0015] In the present example, the spacing layer 104 is removed to
expose the underlying carrier wafer 102 when forming the indented
portion 106. In some examples, however, the indented portion 106
may not extend to the carrier wafer 102. For example, the indented
portion 106 may have a depth that is less than the thickness of the
spacing layer 104. In some examples, instead of using a spacing
layer 104, the indented portion 106 may be formed into the carrier
wafer 102.
[0016] FIG. 1C is a top view 110 of the spacing layer 104.
According to the present example, the indented portion 106 is
rectangular in shape. Additionally, the sloped portions 108 are
formed around all edges of the indented portion 106. The size of
the rectangular indented portion 106 is based on the size of the
photomask to which a pellicle is to be attached. In some examples,
the size of the rectangular indented portion 106 is slightly bigger
than the size of the patterned portion of a photomask. While FIG.
1C illustrates an example for a rectangular mask, other shapes are
contemplated as well. For example, a particular photomask may be
elliptical, circular, square, or have another shape. The indented
portion 106 is designed to match such a shape.
[0017] The top view 110 also illustrates a groove that is patterned
into the spacing layer 104. The groove 109 extends from the
indented portion 106 to the edge of the carrier wafer 102. As will
be described in further detail below, the groove 109 acts as an
exhaust port to allow air within the indented portion 106 to escape
out the sides of the carrier wafer 102. In the example where the
indented portion 106 is formed into the carrier wafer 102 without
use of the spacing layer 104, the groove 109 may also be formed
into the carrier wafer 102.
[0018] FIG. 1D illustrates a pellicle wafer 112 being bonded on the
carrier wafer 102. Specifically, the pellicle wafer 112 is bonded
to the spacing layer 104. In one example, the pellicle wafer 112 is
formed of a semiconductor material such as silicon. The shape of
the pellicle wafer 112 may be substantially similar to the shape of
the carrier wafer 102.
[0019] In one example, the pellicle wafer 112 is bonded to the
spacing layer 104 using a fusion bonding process. Such a bonding
process may involve placing the pellicle wafer 112 against the
spacing layer 104 and applying a high temperature and pressure. For
example, a temperature within a range of about 200-500 degrees
Celsius may be applied. The high temperature causes the material
forming the pellicle wafer 112 to bond with the material forming
the spacing layer 104.
[0020] Bonding the pellicle wafer 112 to the spacing layer 104
creates an open area within the indented portion 106. The open
area, however, is not sealed due to the groove 109 that is formed
within the spacing layer 104. In other words, the open area is in
communication with the environment external to the illustrated
apparatus. In the example where the indented portion 106 is formed
into the carrier wafer 102 without use of the spacing layer 104,
the pellicle wafer 112 is bonded directly to the carrier wafer
102.
[0021] FIG. 1E illustrates the formation of a patterned resist
layer 114. In one example, the resist layer 114 is coated onto the
pellicle wafer 112. The resist layer is then patterned by a
lithography process that includes an exposing process and a
developing process. For example, the resist layer 114 is exposed to
a light source through use of a patterned photomask. After
exposure, certain portions of the resist layer are soluble to a
developing solution. The developing solution thus removes the
soluble portions leaving the patterned resist layer 114 illustrated
in FIG. 1E.
[0022] In some examples, before applying the resist layer, the
backside 103 of the carrier wafer 102 may be thinned down. In some
cases, the combination of the carrier wafer 102, spacing layer 104,
and the pellicle wafer 112 may be too thick to fit into some
photolithography tools. Thus, the carrier wafer 102 may be thinned
down to allow the wafers to fit within the tools that perform the
photolithography processes.
[0023] FIG. 1F illustrates an etching process 116. According to the
present example, an etching process 116 is used to thin down the
pellicle wafer 112 to form a variety of features. The etching
process 116 may be an anisotropic etching process such as a dry
etching process. The portions of the pellicle wafer 112 that are
etched away are the portions that are exposed through the patterned
resist layer 114.
[0024] Etching the pellicle wafer 112 through the exposed portions
of the resist layer 114 creates a variety of features including the
break-off part 118, the pellicle membrane support structure 120,
and the pellicle membrane 122. The pellicle membrane 122 is formed
over the indented portion 106. The pellicle membrane 122 is thin
enough to be substantially transparent to whatever type of light is
to be used with the photomask that is protected by the pellicle
membrane 122, while also being mechanically strong enough to retain
itself. In one example, the pellicle membrane 122 is less than 200
nanometers.
[0025] The pellicle membrane support structure 120 connects the
pellicle membrane 122 to a photomask. More specifically, as will be
described in further detail below, the pellicle membrane support
structure 120 connects the pellicle membrane 122 to a pellicle
frame that is attached to the photomask. From a top view
perspective, the pellicle membrane support structure 120 is a
circuitous structure that follows the rectangular shape of the
indented portion 106.
[0026] The break-off part 118 is positioned between the pelican
membrane support structure 120 and the remaining portions of the
pellicle wafer 112. The break-off part 118 is the formed by forming
a continuous trench that surrounds the pellicle membrane support
structure 120. The break-off part 118 may be similar in thickness
to the pellicle membrane 122. As will be described in further
detail below, the break-off part 118 are designed to be broken
under the application of mechanical pressure in order to disconnect
the pellicle membrane 122 and pellicle membrane support structure
120 from the remaining portion of the pellicle wafer 112. Because
the break-off part 118, pellicle membrane support structure 120,
and pellicle membrane 122 are all formed within the same pellicle
wafer 112, they form a single monolithic structure. In some
examples, the break-off part is vertically aligned with the edge of
the sloped portion 108.
[0027] FIG. 1G is a diagram showing an illustrative top view 150 of
the pellicle wafer 112 after being patterned. The top view 150
shows the pellicle membrane support structure 120 surrounding the
pellicle membrane 122. A continuous trench separates the pellicle
membrane support structure 120 from the remaining portion of the
pellicle wafer 112. The trench forms the break-off part 118.
[0028] FIG. 1H is a diagram showing removal of the patterned resist
layer 114. In one example, the patterned resist layer is removed
using a wet etching process. Such a wet etching process may is
selective so as to remove only the resist layer 114 while leaving
the underlying pellicle wafer 112 substantially intact.
[0029] Additionally, FIG. 1H illustrates a photomask 124 before the
photomask is connected to the pellicle. The photomask 124 includes
a patterned side 125 and a pellicle frame 126. The patterned side
125 may also be referred to as the patterned portion. The patterned
side 125 includes the actual pattern that is intended to be
transferred onto a resist layer of a substrate (not shown) to
manufacture an integrated circuit. The photomask 124 is a
reflective mask. Thus, light from a light source is directed at the
surface of the patterned size. Portions of the patterned side 125
will reflect that light and other portions will absorb that light.
Thus, when the reflected light reaches a resist layer coated on a
semiconductor wafer during a lithography exposing process, the
pattern defined by the patterned side 125 will transfer to that
resist layer.
[0030] The photomask 124 is relatively costly to manufacture.
Moreover, the photomask 124 can be damaged by small particles and
contaminants that will cause defects in the patterns formed through
use of the photomask 124. Such damage is problematic because the
defect may be transferred to thousands of wafers before being
detected. While various cleaning processes may be used to remove
such particles and contaminants, the cleaning process itself may
cause damage to the photomask 124, particularly after repetitive
cleaning cycles. Thus, it is desirable prevent such contaminants
from reaching the patterned side 125 of the photomask 124.
[0031] The pellicle frame 126 may be secured to the photomask 124
in a variety of ways. For example, the pellicle frame 126 may be
bonded to the photomask 124. The pellicle frame 126 may be made of
a metal material such as aluminum or steel. From a top perspective,
the pellicle frame 126 may form a circuitous structure that
encompasses the patterned side 125 of the photomask 124.
Additionally, the pellicle frame 126 may match the size and shape
of the pellicle membrane support structure 120.
[0032] FIG. 1I illustrates the pellicle membrane support structure
120 bonded to the pellicle frame 126. In one example, the bonding
may be achieved through use of silicon glue. As described above,
both the pellicle membrane support structure 120 and the pellicle
frame may have a matching circuitous structure. Thus, by bonding
the pellicle membrane support structure 120 to the pellicle frame
126, a protected area 127 is formed around the patterned side 125
of the photomask 124.
[0033] FIG. 1J illustrates a mechanical force 130 being applied to
the photomask 124 in order to break the break-off part 118 and
disconnect the pellicle membrane and pellicle membrane support
structure 120 from the remaining portions of the pellicle wafer
112. The mechanical pressure may be applied in a variety of
manners. For example, a tool may be used to press against the
photomask 124 and press it downward. The mechanical force 130 is
strong enough to break the break-off part 118 but not so strong as
to damage the pellicle membrane 122 or pellicle membrane support
structure 120.
[0034] The sloped portions 108 of the spacing layer 104 are used to
help the break-off process. Specifically, the mechanical force 130
presses the break-off part 118 against the sloped portions 108. The
width of the break-off part 118 and the slope of the sloped
portions 108 can be tuned to effectively break the break-off part
118. Additionally, as described below, because the spacing layer
104 includes a groove (109, FIG. 1C), the air within the space
within the indented portion 106 can be pushed out through the
exhaust port created by the groove. This prevents pressure from
being applied to the membrane 122. Such pressure may cause damage
to the membrane 122. Thus, the groove 109 optimizes the separation
process.
[0035] FIG. 1K illustrates the photomask 124 with the pellicle 129
separated from the rest of the pellicle wafer 112 and other
structures. The pellicle 129 is a monolithic structure that
includes the pellicle membrane 122 and the pellicle membrane
support structure 120. Using the above described process, the
pellicle 129 also includes a remaining portion 131 of the break-off
part 118. The remaining portion 131 of the break-off part 118 is
coplanar with the pellicle membrane 122 and extends from the
pellicle membrane structure 120 on the opposite side of the
pellicle membrane 122. The remaining portions may have a jagged or
rough edge resulting from the mechanical breaking of the break-off
part 118.
[0036] The pellicle 129 can protect the patterned side 125 of the
photomask 124 from contaminants that may cause damage.
Additionally, the pellicle frame 126 may include features to allow
the pellicle to operate more effectively. For example, the pellicle
frame may allow air to pass between the protected area 127 and the
environment external to the pellicle 129. This is because for some
photolithographic processes, the photomask 124 may be placed in a
vacuum. If the protected area were hermetically sealed, then the
pressure differential between the protected area 127 and the
external environment could put harmful stress on the pellicle
membrane 122 and may even cause it to break. Additionally, the
passageways that allow air to pass between the protected area 127
and the environment external to the pellicle 129 may include a
filter to prevent contaminants and other substances from reaching
the protected area 127 and thus causing damage to the patterned
side 125 of the photomask 124.
[0037] With the pellicle 129 attached, the photomask 124 can be
used to pattern resist layers for integrated circuit fabrication
processes. In one example, Extreme UltraViolet (EUV) light may be
directed at the patterned side 125 of the photomask 124. Such light
will pass through the pellicle membrane 122. Then, after reflecting
off portions of the patterned side 125, the light will again pass
through the pellicle membrane 122 and will ultimately reach the
resist pattern being exposed.
[0038] The above example illustrates the pellicle frame of the
photomask being bonded to the pellicle membrane support structure
before removing the pellicle membrane from the pellicle wafer. In
some examples, however, a mechanical force can be used to
disconnect the pellicle membrane and pellicle membrane support
structure from the pellicle wafer before the pellicle is attached
to the photomask.
[0039] FIG. 2 is a diagram showing illustrative dimensions of a
pellicle 129 and other components used to form the pellicle 129.
According to the present example, the width 202 of the break-off
part 118 may be within a range of about 1-10 millimeters. The width
204 of the pellicle membrane support structure 120 may be within a
range of about 1-10 millimeters. The width 206 of the sloped
portion 108 may be within a range of about 2-20 millimeters. The
slope of the sloped portion 108 is based on the width 206 of the
sloped portion 108 and the thickness of the spacing layer 104. Or,
in the case where the indented portion 106 does not extend down to
the carrier wafer 102, the slope of the sloped portion 108 is based
on the width 206 and the depth of the indented portion 106. As
described above, the sloped portions 108 may not be completely
linear. These dimensions provide sufficient strength to the
pellicle 129 while allowing the break-off part 118 to be
effectively broken without damaging the pellicle membrane 122 or
pellicle membrane support structure 120.
[0040] FIG. 3 is a flowchart showing an illustrative method for
forming a pellicle for a photomask. According to the present
example, the method 300 includes a step 302 for providing a carrier
wafer (e.g. 102, FIG. 1A). As described above, the carrier wafer is
a temporary structure used to support subsequently formed
layers.
[0041] According to the present example, the method 300 further
includes a step 304 for forming a spacing layer (e.g. 104, FIG. 1A)
on the carrier wafer, the spacing layer comprising an indented
portion (e.g. 106, FIG. 1B), the indented portion having a sloped
portion (e.g. 108, FIG. 1B) at an edge of the indented portion. The
spacing layer may be deposited using a high density plasma CVD
process. The spacing layer may be made of a material such as
silicon nitride or silicon oxynitride. The spacing layer can then
be patterned to form the indented portion. An etching process can
be used to remove portions of the spacing layer so as to create the
indented portion. The etching process can also be tuned to create
the sloped portions as desired. As described above, the sloped
portions may be substantially linear, concave, or convex. During
patterning of the spacing layer, a groove may be formed into the
spacing layer that extends from the indented portion to the edge of
the carrier wafer. The groove acts as an exhaust port to allow air
within the indented portion to escape out the sides of the carrier
wafer.
[0042] According to the present example, the method 300 further
includes a step 306 for bonding a pellicle wafer (e.g. 112, FIG.
1D) to the spacing layer so as to form an open area within the
indented portion. The pellicle wafer may be made of a semiconductor
material such as silicon. The pellicle wafer is the piece of
material out of which the pellicle is to be formed.
[0043] In some examples, the backside of the carrier wafer may be
thinned down. In some cases, the combination of the carrier wafer,
spacing layer, and the pellicle wafer may be too thick to fit into
some photolithography tools. Thus, the carrier wafer may be thinned
down to allow the wafers to fit within the tools that perform the
subsequent photolithography processes.
[0044] According to the present example, the method 300 further
includes a step 308 for patterning the pellicle wafer to form a
pellicle membrane (e.g. 122, FIG. 1F) over the indented portion and
a pellicle membrane support structure (e.g., 120, FIG. 1F) over the
sloped portion. This may be done through various photolithographic
techniques. The pellicle membrane is formed by etching away a
portion of the pellicle wafer above the indented portion so that a
thin membrane remains. The pellicle membrane support structure is
formed by etching away portions of the pellicle wafer on both sides
of the region of pellicle wafer that is to form the pellicle
membrane support structure. The pellicle membrane support structure
is formed over the sloped portions.
[0045] The method may also include forming a break-off part. The
break-off part 118 is positioned between the pelican membrane
support structure and the remaining portions of the pellicle wafer.
The break-off part may be similar in thickness to the pellicle
membrane. As will be described in further detail below, the
break-off part are designed to be broken under the application of
mechanical pressure in order to disconnect the pellicle membrane
and pellicle membrane support structure from the remaining portion
of the pellicle wafer. Because the break-off part, pellicle
membrane support structure, and pellicle membrane are all formed
within the same pellicle wafer, they form a single monolithic
structure, which may be referred to as the pellicle.
[0046] According to the present example, the method 300 further
includes a step 310 for bonding a photomask (e.g. 124, FIG. 1H) to
the pellicle membrane support structure. Specifically, the pellicle
membrane support structure is bonded to a pellicle frame that is
attached to the photomask. Such a bonding may be achieved through
use of silicon glue. The pellicle frame may have a rectangular
shape from a top perspective. The pellicle frame is positioned to
encompass the patterned portion of the photomask. The pellicle
membrane support structure may match the shape of the pellicle
frame. Specifically, the pellicle membrane support structure may be
a rectangular, circuitous feature that matches the size and shape
of the pellicle frame. Thus, when bonded to the pellicle frame, the
pellicle membrane support structure, pellicle membrane, and
pellicle frame provided a protected area above the patterned
portion of the photomask.
[0047] According to the present example, the method 300 further
includes a step 310 for applying a mechanical force to disconnect
the pellicle membrane from the pellicle wafer. Specifically, the
mechanical force may push the break-off parts against the sloped
portions to cause them to break. Then, the pellicle, which includes
the pellicle membrane and pellicle membrane support structure, can
be removed. Thus, the pellicle creates a protected area over the
patterned portion of the photomask.
[0048] Using the above described process, the pellicle also
includes a remaining portion of the break-off part. The remaining
portion of the break-off part is coplanar with the pellicle
membrane and extends from the pellicle membrane structure 120 on
the opposite side of the pellicle membrane. The remaining portions
may have a jagged or rough edge resulting from the mechanical
breaking of the break-off part.
[0049] Through use of methods described herein, a pellicle can be
efficiently formed to protect the patterned portion of a photomask.
Thus, the patterned portion of the photomask can be protected from
particles and other contaminants. The pellicle can be formed into a
pellicle wafer and then mechanically disconnected. Such a technique
can efficiently produce an effect pellicle to protect the
photomask.
[0050] According to one example, a method includes providing a
carrier wafer, forming an indented portion on the carrier wafer,
the indented portion having a sloped portion at an edge of the
indented portion, bonding a pellicle wafer on the carrier wafer so
as to form an open area within the indented portion, patterning the
pellicle wafer to form a pellicle membrane over the indented
portion and a pellicle membrane support structure over the sloped
portion, and applying a mechanical force to disconnect the pellicle
membrane from the pellicle wafer.
[0051] According to one example, a method includes forming an
indented portion on a carrier wafer, edges of the indented portion
having a sloped portion sloping from a lower portion of the
indented portion to a top surface of the spacing layer, bonding a
pellicle wafer on the carrier wafer, patterning the pellicle wafer
to form a pellicle membrane over the indented portion, a pellicle
membrane support structure over the sloped portion, and a break-off
part over the sloped portion, applying a mechanical force to break
the break-off part and disconnect the pellicle membrane and
pellicle membrane support structure from the pellicle wafer.
[0052] According to one example, an apparatus includes a photomask
having a patterned portion, a pellicle frame connected to the
photomask, the pellicle frame substantially encompassing the
patterned portion, and a pellicle comprising. A pellicle membrane
support structure shaped according to the pellicle frame, a first
end of the pellicle membrane support structure being bonded to the
pellicle frame, and a pellicle membrane at a second end of the
pellicle membrane support structure, the pellicle membrane
substantially covering the patterned portion.
[0053] The foregoing outlines features of several embodiments so
that those skilled in the art may better understand the aspects of
the present disclosure. Those skilled in the art should appreciate
that they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
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